best budged subwoofer under $300

I'm looking for a good budged subwoofer 300USD max, but i'd like to keep it as low as possible. I've read a lot good reviews about HSU STF-2 but is not in the price range, how's STF-1 compared to STF-2?
Dayton 300-632 seems to be a really cheap subwoofer with good reviews, what do you think?
Used subwoofers are hardly a choice since I live in Mexico and is hard to find someone willing to ship outside US